Building roads



Patented Apr. 29, 1 93 0 FATE ,KARL DAMMANN, or nssnn, GERMANY 1 BUILDING ROADS 1% Drawing. Application filed J'iily 2,1928, Serial No. 290,041, and in Germany July .11, 1927.

.My invention relates to amethod of buildingroads. V.

Theusimplest and cheapest means'to treat ordinary metalledroads so that they res st the influences of the weather and in particular the sucking action of the automobiles consists, as well, known, in applying a tar surfacethereon. 1 According to the experlence hitherto prevailing,this tarring method affords its greatest efiect, if thesmall stones of the ballast layer, to be tarred, lie freely on thesurface of the road, but. are firmly embedded insand or an other binding means. It is however very seldom'that a road is in this condition, at least not to its entire extent. On the contrary, in themost cases the stones are partly coveredby aimud layer or they are loosened, sothat this layeris removed by the trafiic or by means tofsharp brooms; In both cases, however, the effect of the surface tar'ring is doubtful.

But even in the best of cases this thin pro tective-layer obtained by tarringthe'ballast layer in the ordinary manner is not able to resist heavytrjaific for an appreciabletime. For this reason recently the tar layer has been covered, with any fine material bituminized in any suitable manner, to obtain a I stronger wear layer instead of being covered with sand or small rubble. But as experience has shown, required degree ofresistance, if the ballast cover to be tarred does not fulfil the conditions mentioned above.

Therefore with all roads that are exposed to heavy traffic the so-called internal tarring or as'phalting method has been employed 7 hitherto, by either enveloping the ballast stones with bitumenbefore spreading them out, or by subsequently soaking the spread stones with tar or asphalt. The'advantage obtained by this method, however, does not correspond to its-expense, as the sole efiect obtained thereby consists in the fact, that a solid and smooth bottom layer is produced for the wear layer to'be applied thereon as above mentioned. The resistance to wear, however, and thus the life of the road: cover only depends onthis uppermost wear layer,

' method.

:nous binding means this so-called carpet has not the so that the lattermust be renewed time to time. I

Therefore, 'so-called emulsions the ballast has beenpartly filled out with sand or small rubble for economys sake, and only the upper half of the ballast layer emulsion' This is the so-called half-soaking But even in this case the consumption of the comparatively Now my invention constitutes a ifarther step in this direction by not soaking the ballast layer at all. His based upon the perface is protected originally in a suitable mannerfrom the loosening and soiling acsince the employment of the has-been soaked with the costly emulsion is considerable and this method is therefore expensive.

with ordinarysand or thelike tion ofthe traflic, and accordingly a bitumiwithin the layer is' absolutely. superfluous.

It; is far 'more useful to usethe bitumentsaved; in this manner. to produce a satlsfactorily upper wearv layer.

According to my lnvention the interstices with sand or the like; This may be done either by rolling the metalstones into a sand bed or by rinsing the sand in the usual manner with water between the stones during roll ing. In so doing, however, in contradistinction to the-hithertousual mode of construction the stones are not covered with sand, and sand happening to deposit itself on the surface is carefully washed up or swept ofi', sothat of the ballast layer are first completely filled I the surface of the. stones is exposed, Thereupon anordinary surface tar layer is applied to the road with the usual hot taror bitumen.

To this end the road needs not to be absolutely dry, trary, that the surface of the stonesis just beginning to dry., For hot bitumen or) tar adheres very well even to moist stones,provided it has a sufficiently low melting point. Of course, also the above-mentioned expensive emulsions may be used for this surface coat, but this is not necessary, since no penetrationof the applied material in the interit will be sufficient, on the constices is aimed at. But even when emulsion is used, much less emulsion would be consumed due to the interstices previously having been completely filled with sand. Thereupon the surface coat is covered in the usual way with sand or better with small rubble and the road is thoroughly rolled down anew and is then ready for the traffic. The effect of this simple method is very astonishing. The coating material adheres on the surface of the metal stones and penetrates "in the interstices, whereby the stones are supported against one another. The surface hardens and closes itself very quickly and becomes flat as an'as phalt coat. The complete consolidationand tightening of the ballast layer takes place by the traffic without being disturbed by the formation of rolling stones, and the coating 'material resists the sucking action of auto 'mobii'es.

The substantial and efficacious di-fierence between my present method and those hitherto employed thus resides in the fact, that the ballast-layer is not consolidated, previous to its being tarred on the surface, by the traific,

but on the contrary this surface tarring is done at once, when the surface of the stones are exposed and the ballast layer is not yet completely hard. In contradistinction there- 'to,"according to the meaning hitherto prevailing,*the absolute hardness of the ballast to be on-a fresh road cover tarred was the main preliminary condition for the success and this is the case still with all standard road covers. For, with the lattera further compression does not take place, the cover is already completely hard. Now When in that case the'stones havebecome loose having been sucked out,they will not become solid-ag'a-inby tarring or soaking, as the sticking power of the tar or bitumen is insuificient thereforandarepe-ated mutualproppingofthe stones is impossible owingto the hardness of the lower portion of-the ballast. As against this definite compression takes place much more quickly and thoroughly by the traffic produced according to {my invention.

Roads constructed according to my inven '-t1on resemble '1Il appearance and nature the v first class tarred macadam roads and may be permanently maintained in satisfactory condition like these by periodicallytarring them.

True they require a somewhat greater attendance in-maintaining'them, as they at once lose the character of a bituminized road at the places where the thin surface coat is worn out.

Therefore wi'th all more frequented roads it will be of advantage to cover the surface coat, instead of simply applying sand, with a thicker wear layer of a bituminiz'ed fine anine'ral; An easily compressible mass will be particularly that is amass to be applied in cold state,

well suited for this purpose,

the compressing and solidification of which by the traffic takes place in unison with that of the ballast layer. After the compression has been terminated, the ballast layer and the wear coat form a completely coherent, solid and undisplaceable mass the life of which depends only upon the wear by the traffic as that of any first class sand-asphalt cover.

As to the details of execution, my described method maybe modified of course in differ ent respects. As a complete filling of the interstices between the metal stones without soiling their surfaces will not be possible in any weather. Slightly bituminized sand may be used to ultimately fillv the interstices- .In this manner the bituminous protective layer is increased and too much Ltar is. prevented from penetrating into the ballast. 7

Furthermore, to prevent an eventual encess of tar from exuding through the bituminous wear layerand, to save at the same time material for the latter, the tar coat may be first treated with a little sand or rubble, whereuponthe Wear coat is applied. When still greater movement of the ballast of new roads are to be expected due tothe ground giving way, the surface coat is preferably first only sanded and the proper wear layer is applied only later on, when the ground has completely 'come to rest.

In order to obtain an intimate union of the wear layer with the ballast, the latter is preferablytarred slightly before the wear layer is applied thereon.

What I claim and desire ters Patent, is V 1. A method of'constructing roads which consists in superimposing on. a suitable base a layer of metal stones, filling the interstices between the stones with sand, rolling down the said layer, removing the sand from the upper surface of the stones, and'prior to the admission of trafii'c to the surface'of the layer applying directly thereto a compressible layer binding-covering which will be compressed substantially simultaneously with the layerthereunder by the-action of the'traffic subsequently passing 'thereover.

2. A method of constructing roads which consists in superimposing on a suitablebase a layer of metal stones, filling the interstices between the stones with sand, rolling down the said layer, removing thesand from the to secure by Let- 7 upper surface of the stones, and prior to the admission of traffic to the surface of the layer applying directly thereto a covering of'tar which will be compressible substantially simultaneously with the layer thereunder by the action of the traific subsequently passing 'i thereover 8; A method of constructing roadswhich consists in superimposing ona suitable base a layer of metal stones, filling "the interstices between the stones with sand, rolling clown the said layer,

upper surface of the stones, and prior to the admission of trafiic to the surface of the layer applying directly thereto a compressible traflic subsequently passing thereover,

layer binding covering whlch will be 'compressed substantially simultaneously with the layer thereunder by the action of the the compressible covering covsuperimposmg on a further compressible Wear resistin ering whichwill also be compressed sud) tially simultaneouslywith the binding covering and the layer thereunderby the action of trafiic subsequently passing thereover, and finally under such pressure become solid.

4. A method of constructing roads which consists in superimposing on a suitable base filling the interstices a layer of metal stones,

sand, rolling down between the stones with the said layer, removing the sand from the upper surface of the stones, and prior to the admission of trafiic to the surface of the layer applying directly thereto a covering of tar which will be compressible substantially simultaneously with helayer thereundenby the action of thetraffic subsequently passing thereover, and superimposing over the tar with the binding covering a further wear resisting covering of bituminlzed material which will also be compressed substantially simultaneouslycovering and the layer thereunder by the action of traflic subsequently passing thereover, such pressure become'solidp In testimony whereof I aflix my signature.

KARL DAMMANN.

removing the sand fromthe and stanand finally under s 

